1. The Field of the Invention
This invention relates generally to antenna systems, and more particularly, to retractable antenna systems for use in PC Card devices.
2. Present State of the Art
One of the defining characteristics of modem society is the ability to communicate virtually instantaneously over vast distances. Developments in communication technology have freed individuals from the necessity of conducting face to face business transactions. Indeed, with little more than a telephone, and perhaps a computer, an individual can conduct business transactions worldwide through various telephones and/or computer networks.
While the vast web of computer and telephone networks encircling the globe allows almost instantaneous communication between individuals, the communication is generally conducted from place to place and not from person to person. In other words, wired or landline communication networks, such as the telephone network or the Internet, of necessity connect one location to other locations. Thus, when one individual desires to communicate with another individual he or she must locate that individual by telephoning or contacting various locations.
In addition to voice communications over telephone networks, today's communication environment also involves the transfer of vast amounts of digital data over the telephone network or other landline computer networks. Advances in computer technology have placed extremely powerful computers on the desktops of many people throughout the world. Using a telephone or other communication network, these computers can be linked together in order to allow information to be transferred, shared, and exchanged between various individuals. The advent of such technology has opened up broad new possibilities. Taking advantage of such technology, companies have been able to establish remote offices at various locations and conduct business through the sharing and transfer of information over various communication networks.
As computers have continued to become smaller, lighter, and more portable while simultaneously becoming more powerful, the ability of a business executive to take his or her entire "office" on a business trip has become a real possibility. By carrying a small, lightweight, portable computer, and using ordinary telephone lines, an individual may be able to work and share information with the office from virtually any location where access to the telephone network is available. Traditionally, such access has been through landline telephone networks.
From the above description, it is clear that while landline communication networks have created vast opportunities and possibilities for individuals, further advancements and improvements are possible. In many instances the conveniences afforded by a landline communication network are offset somewhat by the inconvenience of being tied to a specific location. Individuals who travel often may find themselves at a location without access to a landline communication network.
In order to overcome these and other problems, wireless communication methods have been developed. Currently, the communications industry is experiencing an explosion of technologies which have been used to build infrastructures to support wireless communications. Major cities throughout the world provide access to cellular communication networks which allow individuals to communicate using wireless cellular telephones. In addition, a dizzying array of beepers and pagers are also available. The trend in all of these markets is towards smaller, more personal communication devices. Since these devices continue to become smaller, and all wireless communication devices must have an antenna system, integration of effective and efficient antenna systems can become problematic. In general, however, antennas which retract inside the housing of the communication device are preferred because such antennas are less prone to breakage and are more compact and elegant in retraction than antennas which remain constantly exposed.
Although many popular devices are directed to voice communications between individuals in the form of cellular telephones or other devices, advances are also being made in wireless data communications. For example, cellular or radio modems which allow a computer to be connected to other computers via a cellular telephone network or other wireless networks can be purchased from many different manufacturers. Obviously, the utility of such a cellular modem is greater with a portable computer than with a non-portable computer.
The most portable computers available today are the small laptop, notebook, and palmtop type computers. Integrating a cellular modem into a small portable computer, however, creates many difficulties. These computers typically have a small form factor and are designed to close up into a relatively small space with clean exterior lines to aid in carrying and transporting the computer. Because wireless communications requires an antenna, one of the major problems encountered when cellular modems are integrated into small portable computers is the integration of the antenna into the computer. Previous attempts to integrate antennas with portable computers have met with only moderate success.
For example, one approach to integrating an antenna with a portable computer is to integrate the antenna into the housing of the computer in much the same way that a cellular telephone antenna is integrated into the housing of the cellular telephone. In other words, a hole can be formed in the housing of the computer and the antenna can be made to retract into, and extend from, the hole. For portable computers using a flip up screen, it may be possible to form this hole along side the screen so that the antenna is in a substantially vertical orientation when the antenna is extended while the computer is being used.
Other attempts to integrate antennas with small portable computers have focused on internal antennas. In these attempts, the antennas are placed inside the computer case so as to be hidden from view. These antennas are typically loop or strip antennas which cannot be extended.
A significant problem with both antennas integrated with the computer case so that they can be extended or retracted into the computer case and with antennas mounted inside the computer case is that computers must be designed around them. Such antenna designs are typically matched to a single type of proprietary computer. Many computer makers are unwilling to commit antenna and wireless modems to hardware platforms given the low percentage of users who will want them. Users would like, ideally, to connect a wireless modem/antenna to a wide variety of computers, including those not specifically designed for wireless communications.
In order to overcome the limitations of the proprietary peripheral ports, the industry has developed standard peripheral slots such as the PC Card standard. This standard, also referred to as the PCMCIA standard, defines a small form factor peripheral about the size of a thick credit card and a corresponding peripheral slot in the portable computer. Peripherals conforming to the PC Card standard can be plugged into any computer having a PC Card slot. The available peripherals include hard disk drives, memory expansion upgrades, landline modems, local area network (LAN) cards, and the like. Most recently, several manufactures have attempted to provide radio modems which loosely conform to the PC Card standard and can be plugged into a PC Card slot. Unfortunately, producing a radio modem for use with a PC Card slot has produced less than satisfactory results.
When installed, standard size PC Cards are generally at least flush with the computers they reside in, and are usually recessed to some degree. When installed, some cards are recessed from the outside of the computer housing by as much as 0.3 inches. Any antenna attached to the PC Card will thus be recessed inside the computer case to some degree. Antennas used to transmit or receive electromagnetic signals perform best if the entire active portion of the antenna is outside of the computer housing during operation. In order to achieve this capability, several manufactures have taken different approaches.
One approach illustrated in FIG. 1 has been to create "extended" PC Card radio modems so that a portion of the PC Card remains outside the housing of the computer. In FIG. 1, the portion of the card residing inside the housing of the computer is labeled 32 and the portion of the card remaining outside the housing of the computer is labeled 30. The antenna 34 is then attached to the portion of the card which remains outside the housing of the computer. In this manner, the antenna not only remains outside the computer, but can also be oriented in the vertical position. In a cellular environment it is believed that an antenna oriented in the vertical position provides better performance than an antenna which is oriented in a horizontal position.
Unfortunately, extended PC Card cards can create several problems. For instance, leaving a portion of the PC Card outside the computer housing destroys the clean lines of the computer. While in transport, the extended card is subject to breakage due to the bumps and rough handling that sometimes accompany transport of a portable computer. In addition, many computers will not fit within their carrying cases with an extended PC Card attached. Thus, in order to transport the computer, the extended PC Card must usually be removed from the computer. This can further subject the extended PC Card to damage through exposure to static electricity or other abuses. Such an arrangement also subjects the extended PC Card to loss, and is inconvenient for the user.
In order to alleviate some of the problems associated with extended PC Card cards, one could have a detachable antenna. An example of such a design is illustrated in FIG. 2. In these designs, the major body of the PC Card 36 remains inside the computer and can be protected by the doors which often cover the PC Card. Along the outside end of the PC Card is a proprietary connector 38 which allows a detachable antenna 40 to be connected to the PC Card. When a user wants to use the cellular modem, the PC Card access door is opened and antenna 40 is attached to PC Card 36 via proprietary connector 38.
Although such a design protects the PC Card and keeps the PC Card inside the machine, the design also creates additional problems. This design suffers from various drawbacks including: 1) the detached antenna can be bulky; 2) the antenna is easily damaged; 3) the antenna is subject to loss; and 4) such an arrangement is inconvenient for the user.
Furthermore, such a design has suboptimal performance. This is because the antenna has a bend in the active portion and attaches to a standard length Type 2 card as shown in FIG. 2. Such an arrangement can leave a portion of the active antenna element inside the computer case. This antenna design would have suboptimal gain.
It would, therefore, represent an advancement in the art to provide a cellular modem in a small form factor, such as the PC Card form factor, which retains the advantages of a clean computer outline for travel and storage, has an antenna whose entire active portion resides outside the computer housing during operation, which has no bends in the active portion, and which does not subject a portion of the cellular modem to loss or damage during storage or transportation of the computer.